hard stop in character joints

Unity Engine
1

Hello- forgive me if this has been covered elsewhere; I did a preliminary search in the forums and didn’t see anything that seemed to address this. I’ve been experimenting with the joint system and this is where I am.

I have a series of spheres (because they are cheap to make) connected like so:

O-o-o-o

where O is kinematic and the rest are character jointed onto the sphere to their immediate left. What I want is to be able to have each joint “bend” say, 30°, within the physics engine. So I set it up as follows:

Axis> X=0; Y=1; Z=0
High Twist Limit> Limit=20; Bouncyness,Spring,Damper=0

I tried giving each of the smaller spheres an Update call such that if space was down they called

rigidbody.SetTorque(0,-50,0);

This works ok, but they overshoot the High Twist Limit. Similarly, when I move the main sphere around they will swing around backwards (and I would like them to hit a “wall” at 0° rotation and lock into place.

Is there a better way to do this? Am I even making sense?

Thanks!

Also, Hi! I am new!

2

No one? I will try and restate the question more simply.

A->B->C (B has a character joint with A as the target, etc for C). The joins have twist limits of 0 for the time being.

When I rotate A, the torque does not change B’s position much (it changes some) but C is clearly bent beyond the constraints that I thought twist limits imposed (if I increase the chain length, they start wrapping around A). I have tried adding bounciness, extremely high spring values (“infinity” seems to break something)… no go: the limits seem to be just vague suggestions.

Is there a way to lock the rotation of a joint at a given value without using a fixed joint? These objects essentially form an arm and I don’t want the elbow to bend backwards, but I do want to be able to bend it forward within the physics engine…

thanks!

3

Hi.

Irc the character joint is not fully implemented. So springs and some other things are not working. If you’re just bending in one axis (like an elbow joint) I would use the hinge joint, it works perfectly. Use the target position of the spring to set the angle you want for the joint.

/Patrik

4

Thanks! I will try that instead.

5

So the hinge joint works better in general I think, but when I stop applying a torque force and they bounce back, they still overshoot the target I set in the spring settings. Is there a way to make it so:

  1. torque is applied to arm
  2. arm hits 30° rotation and stops (no bouncing or overshooting)
  3. torque application ceases
  4. arm returns to 0° (no bouncing or overshooting)

I feel like I could do this with transforms rather than the physics model, but I’d like to impart force when the arm hits something.